Easy open pouch with energy activation

ABSTRACT

The present invention includes a sheet of flexible packaging material that includes one or more films having an inner side and an outer side. On the outer side of at least one film is a pattern of activation particles, preferably metal flakes or the like. The pattern of particles is energy activated causing the pattern to heat and penetrate or weaken at least a portion of the film, creating a tear line in the wall of a package formed from the sheet. A method for creating a tear line in a sheet of flexible packaging material and the formation of the material into a package with a tear line in the side wall or the like is also defined.

TECHNICAL FIELD

The present invention relates to the field of flexible packaging.Particularly, the invention relates to flexible packaging material withan easy-open tear line therein and methods for making a flexiblepackaging material with a tear line.

BACKGROUND OF THE INVENTION

There are a variety of methods used to perforate, score, notch orotherwise create a line of weakness in a flexible packaging material foropening a sealed package. Many of these methods include using caustic oracidic solutions to remove a portion of the material, using mechanicalmeans to cause a line of weakness in the material, and/or re-orientingthe substrate material to improve tear efficiency. These methods oftenproduce a packaging material that includes one or more of the followingdeficiencies: lack of non-linear tear lines in the material, lack ofcross directional tear lines in the material, or high cost.

SUMMARY OF THE INVENTION

One embodiment of the present invention is a sheet of flexible packagingmaterial that includes one or more films having an inner side and anouter side. On the outer side of at least one film is a pattern ofparticles. The particles are exposed to or receive a dose of energycausing them to create heat and penetrate or weaken the film, therebycreating a tear line.

In another embodiment of the present invention, the sheet of flexiblepackaging material with a tear line formed by energy exposed particlesis provided within a package.

In a further embodiment of the present invention a method is providedfor creating a tear line in a sheet of flexible packaging material. Themethod includes providing a sheet that comprises one or more films. Apattern of metal or similar particles is applied on the one side of thesheet or films. The pattern of particles is dosed with an energy sourcecausing the particles to create heat and penetrate into the sheet orfilm material; thus, creating a weakened area and a tear line along theparticle pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there is shown in thedrawings various forms which are presently disclosed; it beingunderstood, however, that this invention is not limited to the precisearrangements and instrumentalities particularly shown.

FIG. 1 is an exaggerated cross sectional view depicting a sheet offlexible packaging material including a film layer and a line ofparticles according to a method of the present invention.

FIG. 2 is an exaggerated cross sectional view depicting a sheet offlexible packaging material including two film layers, with a line ofparticles there-between according to a method of the present invention.

FIG. 3 is a plan view of one form of a flexible package made accordingto the present invention.

FIG. 4 is a perspective view of an alternate flexible package form madeaccording to the present invention.

FIG. 5 is a perspective view of a further alternate form of a packagemade according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, where like numerals identify like elements, there isshown in FIG. 1 a sheet of flexible packaging material, which isgenerally designated by the numeral 10. As used herein, the term “sheetof flexible packaging material” includes materials used in themanufacture of flexible packages (e.g., candy wrappers) and materialsused in covering and/or sealing rigid or semi-rigid containers (e.g.,microwavable dinner containers).

As shown in FIG. 1, the sheet 10 includes a first film layer 14 havingan outer side 16 and an inner side 18. The sheet 10 further includes apattern of particles 12 on the outer side 16 of the film 14. Theparticles 12 are dosed with or exposed to an energy source so as tocreate heat and to penetrate into the surface of the outer side 16 ofthe film 14. The heated penetration of the particles 12 into the film 14weakens the film 14, creating a “tear line”. This weakened area of thefilm is defined herein as a “tear line” regardless of whether theweakened area is in fact linear. The depth at which the energy reactiveparticles penetrate the film after exposure, as shown in FIG. 1, ismerely illustrative and should not be construed to limit the presentinvention.

The sheet 10 can be manufactured using a method of providing the film14, applying a pattern of particles 12 onto the outer side 16 of thefilm 14, and then exposing the pattern to an energy source, thus heatingthe pattern of particles 12 such that the particles 12 weaken theadjacent portions of the film 14 to create a tear line.

The film 14 may include any number of layers or plys and may be made ofone or more of ethylene vinyl alcohol, polyvinyl alcohol, polyethyleneterepthalate, nylon, or a polyolefin. Preferably, one or morepolyolefins are used. Polyolefins are preferred because of theirstrength and because of their normally good tear resistance. Thepolyolefins include, for example, one or more of polypropylene,polyethylene, linear low density polyethylene, and low densitypolyethylene.

The energy reactive particles 12 can be in a variety of forms such asmetal flakes, metallic powders, metal oxides, or derivatives thereof.The particles 12 can have sharp edges to allow for greater and/or easierpenetration into the film wall. The particles 12 may also besubstantially flat or three-dimensional, such as an ellipse, cube orsphere, or be some non-geometric shape.

The size of the particles 12 preferably ranges from about 5 microns toabout 30 microns. More preferably, the particle size is from about 10microns to about 20 microns. When applied to the film, the particles 12are preferably non-uniform in size. Non-uniformity allows for greaterdensity of the particles, because the smaller particles can fill theinterstitial void spaces created by the larger particles.

Preferably, the particles 12 are in the form of metal flakes. Metalflakes have a high aspect ratio such that they are platelet-shaped orsaucer shaped. Different metals can be used for the particles 12. Forexample, the metal particles 12 can be aluminum, nickel, chromium, gold,germanium, copper, silver, titanium, tungsten, platinum, tantalum, andmetal alloys. Preferably, the particles 12 retain or create heat whenexposed to an energy source, such as radio frequency (“RF”), microwavesor the like. Preferably, the particles 12 are aluminum.

To make the particles 12 easier to apply, they can be dispersed in aresin or treated with a solvent to make an ink. The resin serves as anadhesion promoter, allowing the particles to adhere to the film. Thesolvent lowers the viscosity of the ink, making it easier to print ontothe film using conventional printing techniques, such as rotogravure orflexographic. Flexographic and rotogravure printing are well known inthe art and, in the interest of conciseness, will not be described here.The ink containing the metal particles can be front printed or reverseprinted onto the film or a layer or ply within the sheet.

Preferably, the density of the particles 12 in an ink is from about 1%to about 30% loading based on solids, and more preferably from about 5%to about 20% loading based on solids.

The pattern of particles is energy dosed in order for them to createheat and to create the weakness line in the sheet that defines the tearline. Energy dosing can be performed using electron beam (“EB”)radiation, ultraviolet (“UV”) radiation, ultrasonic energy, microwavesor, preferably, radio frequency (“RF”) energy. The energy dose can beapplied to the sheet of flexible packaging as a whole or to only aportion of the sheet or packaging. Preferably, the energy is applied toonly the particles to heat the area of the sheet immediately adjacentthe particles.

When radio frequency is used, the curing energy preferably has afrequency from about 30 gigahertz (“GHz”) to about 300 GHz. Morepreferably, the curing energy has a frequency from about 100 GHz toabout 200 GHz.

Preferably, when the metal particles are exposed to the energy source,they absorb or react to the energy, creating heat. The heat from theparticles then melts or penetrates the film in the area directlyadjacent the particle pattern, weakening the film in that area. Thedepth at which the particles penetrate or otherwise weaken the film willvary depending on several factors. These factors include the type offilm, the thickness of the film, the number of film layers, the numberof co-extruded films, the frequency of the energy at which the particlesare dosed, the type of particles, and the end use of the packagingmaterial (e.g., a package, a cover, or a seal). For example, for a sheetof packaging material including a film of 2 mil thick polyethylene witha pattern of aluminum metal flakes, RF energy can be applied such thatthe depth of penetration is about one thousandth of an inch. This amountof penetration is sufficient to achieve the desired concentratedweakening of the polyethylene film and the desired tearline.

Generally, the energy curing is substantially instantaneous. Forexample, when RF energy is used to cure the metal particles, only abrief exposure (i.e., less than a few seconds) of the energy isnecessary to create the desired tear line. Longer exposure may benecessary for certain metal particles or films, if deeper penetration isdesired.

The energy exposure preferably occurs before the packaging material isformulated into an end product such as a flexible package or acover/seal for a rigid container (See FIG. 5). For sheets of flexiblepackaging material that are stored in a roll, the energy curingpreferably occurs after the flexible material is rolled. For a sheet offlexible packaging material where the particles are between two or morejoined (e.g., laminated or co-extruded) films or layers, the energydosing preferably occurs after the films are joined, but before theflexible material is formed into a package or other similar end product.

Preferably, the particles are positioned such that they will not contactany food product or similar materials that are placed inside the packagecreated from a sheet of flexible packaging material of the presentinvention (e.g., one or more film layers between the metal particles andthe food products or the like). Preventing the food products fromcontacting the metal particles prevents potential contamination.

The sheet 110, as shown in FIG. 2, includes two film layers. An innerside 22 of a second film 20 is joined with the outer side 18 of thefirst film 14. The first film 14 and the second film 20 can bemanufactured such that both of the films include a polyolefin, only oneof the films includes a polyolefin, or neither of the films include apolyolefin. The two films can be joined to create the sheet byco-extrusion, co-polymerization, adhesion or other similar methods.

Although FIG. 2 shows a sheet with two films, it is within the scope ofthe present invention to have a sheet with more than two film layers orplys. When more than two layers or plys are provided, two or more of thefilms can be joined by co-extrusion, co-polymerization, adhesion orother similar methods.

As shown in FIG. 2, the particles 12 are positioned between the outerside 16 of the first film 14 and the inner side 22 of the second film20. The metal particles as shown in FIG. 2 are applied to the outer side16 of the first film 14 such that when the metal particles are dosedwith energy, they penetrate the outer side 16. Alternatively, the metalparticles are applied to the inner side 22 of the second film 20, suchthat when the metal particles are energy dosed, they penetrate the innerside 22. In a further alternative, the application of energy to theparticles causes the metal particles to penetrate both the outer side 16and the inner side 22.

The sheet of packaging material can include graphics. Preferably, thegraphics are printed in a flexographic or rotogravure printing processthat is synchronized with the printing of the particles. The graphicscan be reverse printed on an outside film layer that is joined to thesurface of an underlying film. For example, graphics can be reverseprinted on the inner side 22 of the second film 20.

As an alternative, graphics can be printed on the outside 24 of thesecond film 20 with a coating being applied over the graphics. Suchcoatings include, for example, UV, RF, MW or EB reactive materials, orover lacquers known in the industry. Preferably, the coating is curedusing the same energy source that activates the pattern of particles tocreate the tear line.

As shown in FIGS. 3 and 4, the sheet of packaging material is made intoa package. In FIG. 3, two sheets of flexible packaging material, a firstsheet 10 and a second sheet (not identified), are made into a package 26with a tear line of metal particles 12. The package has sealed seams 28that enclose and seal the contents of the package 26. The package has anoptional tear notch 30. As illustrated, the tear notch 30 is positionedadjacent the tear line created by the particles 12, such that a userstarts the tearing process at notch 30 and continues it along the tearline.

Also as illustrated, the pattern of particles 12 is applied in acontoured shape. Because the particles can be printed on the film in thesame manner as ink is printed, the tear line is not limited to a machinedirection tear of the film. In fact, the tear line can be in any shapethat can be printed onto the film. As shown in FIG. 3, the tear line isin a circular shape to accommodate easy removal of a pull-off coupon 32and the like. The circular tear line allows for a portion of the film(i.e., the pull-off coupon 32) to be removed from the package when tab34, which sits above the film, is pulled.

The package 26 includes an inner side of a first sheet 10 contacting aninner side of a second sheet (not shown). The two sheets are sealedaround all four sides at seams 28 by heated sealing jaws, adhesives orother similar devices.

Alternatively, the package may include only a sheet of packagingmaterial and be configured so as to include a lap seal or a fin seal. Alap seal is formed, for example, when the sheet is slit to anappropriate width, formed into a tubular structure with opposed edgesoverlapped and sealed. Thus, the inside surface of one edge is sealed tothe outside surface of the opposed edge with the seal extendingsubstantially parallel with the adjacent portion of the tubularstructure. A fin seal, on the other hand, is formed when the insidesurface of each opposed edge of the tubular structure are brought intocontact with one another and sealed. Such a seal can extend in adirection independent of the adjacent portion of the tubular structure,and absent folding or other influence, tends to extend perpendicularthereto.

The flexible packaging material can also be formed into a pillow pouch.The sheet is again formed into a tubular structure. The top of thetubular structure and the bottom of the tubular structure are collapsedbetween sealing jaws to form a top end seal and a bottom end seal,respectively. The pillow pouch also includes a longitudinal lap seal,which is formed as described above.

The pillow pouch can be formed, filled and sealed on a vertical orhorizontal form-fill-seal machine. When the pouch is formed on avertical form-fill-seal machine, the laminate is first slit to theappropriate width. The laminate is then fed to the vertical form-filledmachine, which forms the tubular structure, the bottom end seal andlongitudinal lap seal. The pouch is filled with a product prior toforming the top end seal.

Preferably, the adhesive used to seal the packages of the presentinvention is a cold seal cohesive. A cohesive material is defined as amaterial that adheres strongly to another surface of the same materialand only weakly to other materials.

Where two sheets are joined to form the package, the cold seal cohesiveis applied to an inside surface of the first sheet and an inside surfaceof the second sheet. The cold seal cohesive can be a continuous layer,but preferably is pattern-applied at only those places where a seal isto be formed (e.g., around the edges of the first and second sheets).Once the cold seal cohesive is in place, the inside surface of the firstsheet and the inside surface of the second sheet are contacted. The twosheets are then sealed together using sealing jaws or other similardevices.

Alternatively, where the package comprises only a single sheet ofpackaging material, two separate patterns, a first pattern and a secondpattern, of the cold seal cohesive are applied to the single sheet. Insuch an embodiment, the step of forming the package involves sealing thefirst pattern of the cold seal cohesive on the sheet with a secondpattern of a cold seal cohesive on the sheet. As described above, theseal can be an end seal, a lap seal, a fin seal or the like, and mayinclude, if desired, a notch at the edge of the package for starting thetearing of the film.

The advantages of pattern-applying the cold seal cohesive include thefact that far less cold seal cohesive is necessary and that the coldseal cohesive does not contact the contents of the package, or does soonly along very narrow areas at the seams. Pattern-applying the coldseal will be necessary for some uses, especially food uses, where morethan minimal contact between the contents of the package and the coldseal cohesive will not be acceptable.

Preferably, the machine for applying the cold seal cohesive is aflexographic or rotogravure printing machine forming part of the sameproduction line as, and is mechanically synchronized with, the machineused for the printing of the particles. Such synchronization providesfor an efficient packaging process.

The cold seal cohesive can be based on rubber latex, but is preferablybased on uncured isoprene or styrene butadiene rubber. These syntheticrubbers are more stable than natural rubber, allowing a material with alonger life, are more consistent, and do not present the risk ofallergic reactions, and even anaphylactic shock, experienced by somepeople with natural latex products.

Alternatively, the seams of the package can be sealed with a hot meltadhesive. A package with seams sealed with a hot melt adhesive can bemanufactured as described above. For example, the sheet of packagingmaterial 10 can be wrapped into a tubular structure with overlappingopposed edges. The overlap can be formed by contacting the inner side 16and the outer side 18. A bead, in the form of a line or one or moredrops, of hotmelt adhesive can be applied to one of the edges in orderto join the overlapping edges. The joined edges are then sealed withsealing jaws or other similar devices to create a heat sealed seam.

Flexible packaging made from the sheet of flexible packaging material 10can be in various forms. As shown in FIG. 4, the sheet of flexiblepackaging material is formed into a flexible, air-tight package 36. Thepackage 36 includes sheets of packaging material with one or more joinedfilms sealed along one or more seams. The package 36 includes a sheet 10with metal particles 12, which, when cured, create a tear line. Thepackage 36 also includes an optional tear notch 30 that is adjacent thetear line. The tear line provides for an easy opening package. Theoptional tear notch 30 aids in the ease of opening the package byproviding a starting point for tearing.

The package 36 can be used to hold various air-perishable products suchas meats, cheeses, coffee, chips, nuts, and other foodstuffs. After theproducts are inserted into the package, the package can be exposed to avacuum so that the contents of the package are not exposed to thedegradation effects of air. Consequently, the packaged products can havea shelf life comparable to rigid packages (e.g., jars or cans).

With the flexible airtight package 36, the tear line serves as aweakened area, allowing a user to open the package more easily. Tomaintain the airtight nature of the package 36, the depth to which theparticles penetrate is such that the tear line does not adversely affectthe barrier properties of the package.

The flexible packaging of the present invention is not limited toair-tight packages. Rather, the flexible packaging can be formed into anon air-tight pouch or wrapper, for example, a pouch or wrapper for foodarticles such as fruits and vegetables.

In a non air-tight package, the tear line not only allows a user to openthe package more easily, but it also can provide a “breathable” area inthe package. As used herein “breathable” means allowing oxygen and/orwater vapor transmission through the packaging material. The rate atwhich oxygen passes through the material is termed the oxygentransmission rate, and can be measured by standard means known in theindustry. The rate at which the water vapor passes through the materialis termed the water vapor transmission rate, and it also can be measuredby standard means known in the industry.

To create a breathable area in the package, the particles must penetratethe film to such depths that oxygen and/or water vapor can betransmitted through the tear line. To create a breathable area, it ispreferred that the packaging material include a thermoplastic materialthat will soften more than other materials when exposed to the energydose and the heat of the particles.

Flexible packaging, whether it is an air-tight package or another type,provides numerous advantages over rigid packages. For example, flexiblepackages can be manufactured at a lower cost than rigid packages and aregenerally substantially lighter in weight than rigid packages. Further,flexible packages can be stored flat, reducing the amount of storagespace required for unfilled packages.

As shown in FIG. 5, a sheet of flexible packaging material 210 forms acover for a substantially rigid container 214, such as a microwavabledinner package 208. A pattern of particles 212 to be energy dosed tocreate a tear line in the wall 210 covering the top of the container215. The pattern of particles 212 is applied such that a user can easilyremove a portion of the cover sheet 210 to expose a food product A(e.g., apple sauce) that is to be cooked uncovered. This allows foodproducts B, C and D (e.g., stuffing, peas, turkey) to be covered bysheet 210 during cooking.

It will be appreciated by those skilled in the art, that the presentinvention may be practiced in various alternate forms andconfigurations. The previously detailed description of the disclosedembodiments is presented for purposes of clarity of understanding only,and no unnecessary limitations should be implied there from.

1. A sheet of flexible packaging material comprising: a first filmlayer, the film comprising an inner side and an outer side; and a tearline on the outer side of the film, the tear line comprising an energydosed pattern of particles penetrated into the outer side of the film.2. A sheet of flexible packaging material according to claim 1 whereinthe sheet further comprises an inner side of a second film joined to theouter side of the first film.
 3. A sheet of flexible packaging materialaccording to claim 2 wherein the second film and the first film areco-extruded.
 4. A sheet of flexible packaging material according toclaim 1, wherein the film comprises a polyolefin.
 5. A sheet of flexiblepackaging material according to claim 4 wherein the film is selectedfrom the group consisting of polypropylene, polyethylene, linear lowdensity polyethylene, and low density polyethylene.
 6. A sheet offlexible packaging material according to claim 1 wherein the particlesare made of a metal material.
 7. A sheet of flexible packaging materialaccording to claim 6 wherein the metal particles are from about 5microns to about 30 microns in size.
 8. A sheet of flexible packagingmaterial according to claim 6 wherein the metal particles comprisealuminum flakes.
 9. A sheet of flexible packaging material according toclaim 1 wherein the particles are formed in a non-linear pattern.
 10. Asheet of flexible packaging material according to claim 1 wherein theparticles of the tear line are dispersed in an ink.
 11. A sheet offlexible packaging material according to claim 1 wherein the particlesare activated by radio frequency energy.
 12. A sheet of flexiblepackaging material according to claim 11 wherein the radio frequency isfrom about 30 gigahertz to about 300 gigahertz.
 13. A sheet of flexiblepackaging material according to claim 1 wherein the particles areexposed to an ultrasound energy source.
 14. A flexible packagecomprising: a sheet of flexible packaging material according to claim 1formed into a tubular structure with a bottom end and a top end; a seamformed along the bottom end, a seam along the top end, and alongitudinal seam along a length of the package, wherein the seamsenclose the package.
 15. A method for making a sheet of flexiblepackaging material with a tear line, the method comprising: providing afirst film, the film comprising an inner side and an outer side;applying a pattern of activation particles on the outer side of thefilm; and exposing the pattern of activation particles to an energysource, causing the particles to heat and weaken the film adjacent theparticle pattern and to create the tear line.
 16. A method according toclaim 15 wherein the particles are exposed to radio frequency energy.17. A method according to claim 16 wherein the radio frequency is fromabout 30 gigahertz to about 300 gigahertz.
 18. A method according toclaim 15 wherein the particles comprise metal flakes.
 19. A methodaccording to claim 15 wherein the particles comprise aluminum.
 20. Amethod for forming a package with a tear line, the method comprising:providing at least one sheet of flexible packaging material producedaccording to the method of claim 15; forming the sheet into a tubularstructure with a bottom end and a top end; sealing a seam along thebottom end and sealing a longitudinal seam along a length of the tubularstructure; filling the package with a product from the top end, theproduct contacting the inner side of the sheet; and sealing the top endto enclose the product.
 21. A method according to claim 20 wherein theseams are sealed by a cold seal cohesive.
 22. A method according toclaim 20 wherein the seams are sealed with a hot melt adhesive.